1. Field of the Invention
The present invention relates to a capacitance sensing apparatus and a touchscreen apparatus.
2. Description of the Related Art
A touch sensing apparatus such as a touchscreen, a touch pad, or the like, an input apparatus attached to a display apparatus to provide an intuitive data input method to a user, has recently been widely used in various electronic devices such as cellular phones, personal digital assistants (PDAs), navigation devices, and the like. Particularly, as demand for smartphones has recently increased, the use of touchscreens as touch sensing apparatuses capable of providing various data input methods in a limited area has correspondingly increased.
Touchscreens used in portable devices may be mainly divided into resistive type touchscreens and capacitive type touchscreens, according to a method of sensing a touch input utilized thereby. Here, capacitive type touchscreens have advantages in that they have relatively long lifespans and various data input methods and gestures may easily implemented therewith, such that the use thereof has correspondingly increased. Particularly, a multi-touch interface may be more easily implemented in capacitive type touchscreens as compared to resistive type touchscreens, such that capacitive type touchscreens are widely used in devices such as smartphones, and the like.
Capacitive type touchscreens include a plurality of electrodes having a predetermined pattern and defining a plurality of nodes at which a change in capacitance is generated by a touch input. In the plurality of nodes distributed on a two-dimensional plane, a change in self capacitance or a change in mutual capacitance is generated by the touch input. Coordinates of the touch input may be calculated by applying a weighted average method, or the like, to the change in capacitance generated in the plurality of nodes. In order to accurately calculate the coordinate of the touch input, technology capable of accurately sensing the change in capacitance generated by the touch input is required. However, in the case in which electrical noise is generated in a wireless communications module, a display apparatus, or the like, it may hinder the change in capacitance from being accurately sensed. In addition, an offset value that becomes a reference in determining the touch input should be continuously accurately set, according to an operational environment, and a touch input intended by the user may be erroneously recognized in the case in which the offset value is erroneously set due to foreign objects present in a panel unit, an unintended touch operation of the user, and the like.
The following Related Art Document (Patent Document 1), which relates to a touchscreen apparatus and a noise removing method thereof, discloses a feature of removing noise using an offset calculated by averaging low data, but fails to disclose a feature of integrating a change in capacitance generated in a touch panel twice in positive (+) and negative (−) directions during a single period of a driving signal to remove common noise and amplifying the integrated voltage to generate offset information.